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Check Unnecessary Nullable Parameters

danger

This command is deprecated and will be removed in 1.18.0.

Consider migrating to "dcm check-parameters".

Checks unnecessary nullable parameters in functions, methods, constructors. Removing unnecessary nullables can help reduce amount of checks in the code.

To execute the command, run:

$ dcm check-unnecessary-nullable lib # or dcm un lib

Full command description:

Usage: dcm check-unnecessary-nullable [arguments] <directories>
-h, --help                                       Print this usage information.


-r, --reporter=<console>                         Analysis output format.
                                                 [console (default), json, codeclimate, gitlab, checkstyle]
-a, --absolute-path                              Show absolute paths in console reporter output.
    --json-path=<path/to/file.json>              Path to the JSON file with the analysis output.


-c, --print-config                               Print resolved config.


    --root-folder=<./>                           Root folder.
                                                 (defaults to the current directory)
    --sdk-path=<directory-path>                  Dart SDK directory path.
                                                 If the project has a `.fvm/flutter_sdk` symlink, it will be used if the SDK is not found.
    --exclude=<{**/*.g.dart,**/*.freezed.dart}>  File paths in Glob syntax to be exclude.
                                                 (defaults to "{**/*.g.dart,**/*.freezed.dart}")


    --no-congratulate                            Don't show output even when there are no issues.


    --verbose                                    Show verbose logs.


    --ci-key                                     The license key to run on CI server. Can be provided via DCM_CI_KEY env variable.
    --email                                      The email used to purchase the license. Can be provided via DCM_EMAIL env variable.


    --no-analytics                               Disable sending anonymous usage statistics.


    --monorepo                                   Include publicly exported code into the check.


    --[no-]fatal-found                           Treat found unnecessary nullable parameters as fatal.
                                                 (defaults to on)

Suppressing the command​

In order to suppress the command add the ignore: unnecessary-nullable comment. To suppress for an entire file add ignore_for_file: unnecessary-nullable to the beginning of a file.

Monorepo support​

warning

By default, this command treats all code that is exported from the package as used. It uses check-exports-completeness results and won't report even transitive public entities that are not exported directly.

This command also follows this convention of locating implementation files in the lib/src/ folder. If you don't follow this convention, you will need to pass the --monorepo flag for this command to work.

To disable this behavior use --monorepo flag. This might be useful when all the packages in your repository are only used within the repository and are not published to the pub.

Output example​

Console​

Use --reporter=console to enable this format.

Console

JSON​

The reporter prints a single JSON object containing meta information and the unnecessary nullable parameters. Use --reporter=json to enable this format.

The root object fields are​

  • formatVersion - an integer representing the format version (will be incremented each time the serialization format changes)
  • timestamp - a creation time of the report in YYYY-MM-DD HH:MM:SS format
  • unnecessaryNullable - an array of unnecessary nullable issues
{
  "formatVersion": 2,
  "timestamp": "2021-04-11 14:44:42",
  "unnecessaryNullable": [
    {
      ...
    },
    {
      ...
    },
    {
      ...
    }
  ]
}

The unnecessaryNullable object fields are​

  • path - a relative path of the file with unnecessary nullable parameters declaration
  • issues - an array of issues detected in the target class
{
  "path": "lib/src/some/class.dart",
  "issues": [
    ...
  ],
}

The issue object fields are​

  • declarationName - the name of a declaration with unnecessary nullable parameters
  • declarationType - the type of a declaration with unnecessary nullable parameters (function, method or constructor)
  • parameters - an array of strings representing parameters that are marked as nullable
  • offset - a zero-based offset of the class member location in the source
  • line - a zero-based line of the class member location in the source
  • column - a zero-based column of class member the location in the source
{
  "declarationName": "someFunction",
  "declarationType": "function",
  "parameters": "[String? value]",
  "offset": 156,
  "line": 7,
  "column": 1
}

GitLab​

Reports unnecessary nullable issues in merge requests based on Code Quality custom tool. Use --reporter=gitlab to enable this format.

Checkstyle​

Use --reporter=checkstyle to enable this format.

<?xml version="1.0"?>
<checkstyle version="10.0">
  <file name="../abstract_class.dart">
    <error line="0" severity="warning" message="function myFunction has unnecessary nullable parameters" source="unnecessary-nullable-issue"/>
  </file>
  <file name="../class_with_factory_constructors.dart">
    <error line="0" severity="warning" message="function myOtherFunction has unnecessary nullable parameters" source="unnecessary-nullable-issue"/>
  </file>
</checkstyle>